Notwithstanding anything hereinbefore contained, the Trustees may, if they think fit, with the previous sanction of the Central Government and subject in each case to such conditions as it may approve and to such rules as it may prescribe, assume the custody and administration of collections which are not the property of the Trustees for the purposes of their trust under this Act, and keep and preserve such collections either in the Indian Museum or elsewhere:
     Provided that if the trust constituted by this Act is at any time determined, any such collections shall not by reason of their then being in the Indian Museum become the property of Government.